Human procalcitonin and the preparation and use thereof

ABSTRACT

The invention relates to human procalcitonin and the preparation and use thereof. In particular, a process for preparing human procalcitonin is described wherein a gene coding for a polypeptide comprising the amino acid sequence of human procalcitonin is inserted into a vector; a host organism is transformed with this gene-containing vector; and the polypeptide expressed by the host organism is isolated. Furthermore the use of the polypeptides according to the invention, in particular as medicaments and diagnostic agents is described.

[0001] The invention relates to human procalcitonin and the preparation,in particular by genetic engineering processes, and use thereof.

[0002] Procalcitonin (“pCT”) is a protein consisting of 116 amino acidsand having a molecular weight of about 13,000 dalton. It is theprohormone of calcitonin which under normal metabolic conditions isproduced and secreted by the C cells of the thyroid. pCT and calcitoninsynthesis is initiated by translation of preprocalcitonin (“pre-pCT”), aprecursor peptide comprising 141 amino acids. The amino acid sequence ofhuman pre-pCT was described by Moullec et al. in FEBS Letters, 167:93-97in 1984. pCT is formed after cleavage of the signal peptide (first 25amino acids of pre-pCT). In healthy people the hormone calcitonin (aminoacids 60-91 of the pCT amino acid sequence), and N-procalcitonin (aminoacids 1-57 of the pCT amino acid sequence) and katacalcin (amino acids96-116 of the pCT amino acid sequence) are produced intracellularly frompCT by specific proteolysis (see also Conlan et al. (1988) Biochem. J.,256:245-250). pCT and fragments thereof were detected in increasedconcentrations in the serum or plasma of patients, in particular incases of certain neoplastic diseases (Ghillani et al. (1989) CancerResearch, 49:6845-6851) and sepsis (EP-B1-0 656 121) and SIRS (systemicinflammatory response syndrome) (Snider et al., (1997) J. Investig.Med., 45:552-560).

[0003] During the typical sepsis bacteria are released continuously orin phases from a focus into the bloodstream. Endotoxin or otherpyrogenic and toxic substances interacting with body mechanisms causethe clinical manifestations. The acute onset triggers chills and insevere cases a shock reaction. Special forms of septic shock areWaterhouse-Friderichsen syndrome and toxic shock syndrome (TSS). TSS isknown as an acute clinical picture in staphylococcal infections which iscaused by a specific staphylococcal toxin. A severe sepsis quitefrequently develops in patients with serious primary disorders such as,for example, neoplastic diseases, serious burns and traumas.

[0004] The importance for sepsis diagnosis of detecting pathogens in theblood (“positive blood culture, bacteremia”) has been pushed into thebackground, because in general the blood culture is positive only in 20to 40% of sepsis cases. The term sepsis has therefore undergone achange. The modern term “sepsis” describes a clinical syndrome which ingeneral comprises fever, leukocytosis, alterations of consciousness, ahyperdynamic circulation (“warm shock”) and a hypermetabolic state, apositive blood culture no longer being required as a prerequisite forsepsis diagnosis.

[0005] WO 98/33524 suggests employing antibodies binding to pCT for thetherapy of sepsis and SIRS.

[0006] Over many years polyclonal antibodies were obtained fromimmunization by calcitonin and used for detecting so-calledimmunoreactive calcitonin which aside from calcitonin also comprisesprocalcitonin and further procalcitonin fragments. Immunization bysynthetic peptides having amino acid sequences corresponding to thesequences of procalcitonin segments succeeded in producing variousmonoclonal antibodies binding to various calcitonin and katacalcinepitopes (Ghillani et al. (1988) J. Immunol., 141:3156-3163).

[0007] On the basis of these antibodies sandwich immunoassays fordetecting pCT and calcitonin in serum samples were also developed. Acombination of an anti-katacalcin antibody and an anti-calcitoninantibody was suggested for detecting calcitonin precursor molecules. Asynthetic peptide suited to these antibodies was employed as standardmaterial.

[0008] It is known that in immunochemical tests the measured signals forstandards and samples need not necessarily be identical even if theamount of antigen is exactly the same. If standard and sample antigensare not really identical regarding their immunochemical reactivity, theantibodies employed in the test will recognize either the one or theother antigen better. This leads in the end to different measuredsignals for samples and standards.

[0009] It follows from this that the use as standard antigen of antigenfragments instead of the whole protein is often associated withdisadvantages and can, in particular, lead to distorted measurements.Furthermore, it is in general not possible for the epitopes based on thethree-dimensional structure of the correctly folded protein to becorrectly represented by shorter peptides. This results in it not beingpossible to obtain antibodies against such conformation epitopes on useof peptides as immunogens. It is advantageous especially in competitivetest formats if the substance to be detected has the same immunochemicalreactivity as the corresponding solid phase or label-bound test reagent.

[0010] Although the complete amino acid sequence of human pCT has nowbeen known since 1984, so far human pCT has not been preparedsuccessfully, in particular not in relatively large amounts andreproducibly. So far only murine pCT could be expressed in E. coli bymeans of genetic engineering processes (Rehli et al. (1996) Biochem.Biophys. Res. Com., 226:420-425). However, murine pCT differs from humanpCT to such an extent (about 77% homology at the amino acid level) thatit is still an object for the skilled worker to develop a process bywhich human pCT can be produced in relatively large amounts, costeffectively and in isolated form in order to be able to employ itparticularly as an immunogen and/or standard and control sera antigen.

[0011] This object is achieved by providing the polypeptides accordingto the invention described in claims 1-3, the plasmids according to theinvention described in claims 10 and 11, the cells according to theinvention described in claim 12 and the preparation processes accordingto the invention described in claims 4-9. The polypeptides according tothe invention, i.e. the polypeptides as claimed in one of claims 1-3 orthe products of a process as claimed in claims 4-9, can be employedusefully in particular in the fields of diagnosis and therapy. Preferredembodiments of the invention are disclosed in claims 13-23. Furthermore,the polypeptides according to the invention can be used for immunizationto obtain the antibodies according to the invention. A furtherembodiment of the invention is the pCT solutions described in claims24-29.

[0012] It was not possible to predict the feasibility of human pCTexpression according to the invention: pCT is expressed in the cell notas pCT, but originates from preprocalcitonin by proteolytic cleavage ofthe N-terminal signal peptide. It had to be assumed that in eukaryotespCT without signal peptide is not expressed in the natural cellcompartment and folds in a different way, potentially causing biologicalinactivation and possibly even instability. In addition, theheterologous expression in E. coli instead of the natural expression inanimal cells and the expression attempted within the framework of theinvention of a fusion protein of procalcitonin and the artificialsequence MRGSHHHHHHGS N-terminally therefrom could not be foreseen asprospectively successful. Although expression in E. coli of murine pCTas a poly-His fusion protein has been described in the literature (Rehliet al.), no conclusions can be drawn from this for the feasibility ofhuman pCT expression since there is only about 77% identity at the aminoacid level and therefore a completely different behavior must beexpected. Furthermore, the murine pCT was not expressed directly afterthe putative signal peptide cleavage site (A25/V26) (Jakobs et al.,1981, Science, 213:457-459), but only a murine procalcitonin fragmentshortened by 7 amino acids was expressed, which again may haveunforeseeable consequences for the expressibility. Finally, thepublication contains neither the exact fermentation conditions nor theachievable yields after purification of the fusion protein.

[0013] In the following specific embodiments of the invention aredescribed in more detail:

[0014] The invention relates preferably to an isolated polypeptidecomprising the amino acid sequence of human pCT, in particular ifprepared using genetic engineering processes. The amino acid sequence ofhuman pCT is shown in FIG. 1.

[0015] The term “genetic engineering processes” in accordance with thisinvention also means in particular processes in which the polypeptide tobe expressed is produced by eukaryotic or prokaryotic cells, the nucleicacid sequence coding for the polypeptide to be expressed and includingrecombinant nucleic acid sequences being introduced previously intothese cells, for example by means of vectors, liposomes, projectiles orco-precipitation with salts. In another process a gene already naturallypresent in the cell and coding for the polypeptide to be expressed isactivated by activating measures, for example by gene amplification oractivation by means of artificially introduced promoter and/or enhancersequences or deletion of repressor binding sequences such that the cellexpresses the polypeptide to be expressed in larger amounts thannaturally.

[0016] The term “amino acid sequence of human pCT” in accordance withthis invention also means amino acid sequences slightly altered byexchange, deletion or addition of amino acids, and these alterationsshould have no serious negative influence on the binding properties ofthe polypeptide towards anti-pCT antibodies. The skilled worker cancheck this on the basis of appropriate binding studies using availableanti-pCT antibodies.

[0017] The term “peptides” in accordance with this invention comprisesamides which decompose into amino acids on hydrolysis, for example aminoacid polymers such as, for example, polypeptides, oligopeptides,proteins or protein fragments. Molecules with no more than ten linkedamino acids are in general called oligopeptides, with more than thatthey are called polypeptides.

[0018] Further polypeptides according to the invention are isolatedpolypeptides which contain the amino acid sequence shown in FIG. 2A or2B and which have preferably been prepared using genetic engineeringprocesses.

[0019] A preferred process according to the invention is a process forthe preparation of human procalcitonin wherein (i) a gene coding for apolypeptide comprising the amino acid sequence of human procalcitonin isinserted into a vector, (ii) a host organism is transformed with thisgene-containing vector and (iii) the polypeptide expressed by the hostorganism is isolated. Preferred variant of this process according to theinvention are those preparing a polypeptide having the amino acidsequence according to FIG. 1, 2A or 2B.

[0020] A “vector” is in particular a DNA or RNA molecule which iscapable of replication in a host organism and from which a recombinantDNA or RNA molecule can be constructed by incorporation of one or moreforeign genes. Examples of common vectors are bacterial plasmids; viralgenomes, in particular genomes of bacteriophages; yeast chromosomes andplasmids, in particular YEp, YIp, YRp, YAC; Ti plasmid; and vectorsderived from adenoviruses, papillomaviruses and retroviruses. In orderto facilitate expression of a foreign gene a vector in general has apromoter which is, if possible, physically or chemically inducible andwhich initiates transcription of a messenger RNA coding for the proteinto be expressed. Furthermore a vector in general has a nucleic acidsequence causing a transcription stop and nucleic acid sequences causinga very efficient translation such as, for example, a ribosome bindingsite in the case of bacterial expression. Additionally an expressionvector should have translation stop sequences in all possible readingframes.

[0021] Particularly preferred processes according to the inventioncomprise the vector, for example pQE-30, coding for a fusion segment,preferably polyhistidine, which later on permits a simple purificationof the procalcitonin fusion protein.

[0022] Suitable host cells for the process according to the inventionare human, animal, plant or prokaryotic cells; particularly preferredare E. coli cells.

[0023] A “fusion protein” in accordance with this invention means aprotein which comprises pCT and a further either C- or N-terminal poly-or oligopeptide which is translated in its entirety as one polypeptide.The fusion segment preferably ought to either increase theexpressibility of procalcitonin and/or facilitate a later simplepurification by affinity chromatography of the fusion protein.

[0024] Preferably the processes according to the invention will employmetal affinity chromatography and/or gel filtration to isolate thepolypeptide according to the invention.

[0025] Metal affinity chromatography makes use of the fact that achromatography gel matrix containing chelated doubly charged metal ions,for example Ni²⁺, which still have a plurality of freely accessiblecoordination sites can bind reversibly to proteins containing aplurality of histidines in succession. Elution of the polyhistidinepolypeptide under mild conditions may then be achieved competitively,for example by imidazole-containing buffers.

[0026] This invention further relates to a plasmid containing one ormore nucleic acid sequences coding for one or more of the polypeptidesaccording to the invention. A very particularly preferred plasmidaccording to the invention named internally pQE-PCT was deposited underdeposition number DSM 13203 at the DSMZ Deutsche Sammlung vonMikroorganismen und Zellkulturen GmbH, Mascheroder Weg 1b, Braunschweig,Germany on Dec. 16, 1999.

[0027] A further embodiment according to the invention are animal,plant, isolated human or prokaryotic cells which can express one or morepolypeptides according to the invention.

[0028] Yet another embodiment of this invention is the use of thepolypeptides according to the invention as immunogens for preparingantibodies. The process according to the invention for preparingantibodies comprises the use as immunization antigen of one or morepolypeptides according to the invention. Antibodies obtained by means ofthis process are called “antibodies according to the invention”hereinafter.

[0029] The term “antibody” in accordance with this invention means animmunoglobulin, for example an immunoglobulin of the class or subclassIgA, IgD, IgE, IgG₁, IgG_(2a), IgG_(2b), IgG₃, IgG₄, IgM. An antibodycomprises at least one binding site (often called paratope) for anepitope (often-also called antigenic determinant) on an antigen orhapten. Such an epitope is characterized, for example, by itsthree-dimensional structure and/or the presence of polar, and/or apolargroups. The antibody binding site is complementary to the epitope. Theantigen-antibody reaction or hapten-antibody reaction works according tothe so-called “lock-and-key principle” and is in general specific to ahigh degree, i.e. the antibodies are capable of distinguishing smalldifferences in primary structure, charge, three-dimensionalconfiguration and steric arrangement of the antigen or hapten. Inparticular the so-called complementarity determining regions of theantibody contribute to the binding of the antibody to the antigen orhapten.

[0030] The term “antigen” comprises monovalent and polyvalent antigens.A polyvalent antigen is a molecule or a molecule complex to which morethan one immunoglobulin can bind simultaneously, whereas only a singleantibody can bind to a monovalent antigen at any one time. A haptenusually denotes a molecule which on its own is not immunogenic but isusually bound to a carrier for immunization purposes.

[0031] The term antibody in accordance with this invention means notonly complete antibodies but expressly also antibody fragments such as,for example, Fab, Fv, F(ab′)₂, Fab′; and also chimeric, humanized, bi-or oligo-specific or single-chain antibodies; furthermore alsoaggregates, polymers and conjugates of immunoglobulins and/or fragmentsthereof as long as the binding properties to the antigen or hapten aremaintained. Antibody fragments can be prepared for example by enzymaticcleavage of antibodies using enzymes such as pepsin or papain. Antibodyaggregates, polymers and conjugates can be generated by a multiplicityof methods, for example by heat treatment, reaction with substances suchas glutaraldehyde, reaction with immunoglobulin-binding molecules,biotinylation of antibodies and subsequent reaction with streptavidin oravidin, etc.

[0032] An antibody in accordance with this invention can be a monoclonalor a polyclonal antibody. The antibody may have been prepared accordingto the usual processes, for example by immunization of man or an animalsuch as, for example, mouse, rat, guinea pig, rabbit, horse, sheep,goat, chicken (see also Messerschmid (1996) BIOforum, 11:500-502) andsubsequent preparation of the antiserum; or by establishing hybridomacells and subsequent purification of the secreted antibodies; or bycloning and expression of nucleotide sequences or modified versionsthereof coding for amino acid sequences which are responsible forbinding of the natural antibody to the antigen and/or hapten.

[0033] In a preferred embodiment of the process according to theinvention the polypeptides according to the invention which are used asimmunization antigens may be used for the immunization in unbound and/orcarrier-bound form. Typical carriers are, for example, proteins such as,for example, ovalbumin, albumin or hemocyanin, or polymers such as, forexample, polyethylene glycol, polyacrylamide orpoly-d-glutamine-d-lysine. The polypeptides can be bound to thiscarrier, for example, using carbodiimide or glutaraldehyde or else abifunctional reagent which can also act as a spacer (for examples andcoupling methods see e.g. Wong S. (1993) Chemistry of ProteinConjugation and Cross-linking, CRC Press Inc., Boca Raton).

[0034] The immunization antigen, for example, may be suspended inphosphate-buffered saline and treated with Freund's adjuvant. Thisemulsion may then be administered, for example, intradermally,intraperitoneally and/or subcutaneously to an animal, for example arabbit, mouse, rat, guinea pig, horse, sheep, goat, chicken, etc.Booster injections may help to increase the immune response, it alsobeing possible for the immunization antigen to be emulsified withincomplete Freund's adjuvant.

[0035] Polyclonal antibodies according to the invention may be obtainedfrom the antiserum of the immunized animals. These antibodies can befurther purified by means of affinity chromatography on a matrix towhich, for example, pCT or pCT fragments have been bound.

[0036] In order to create monoclonal antibodies according to theinvention the immune cells of immunized animals such as, for example, amouse, are fused according to generally well-known methods (see e.g.Harlow & Lane (1988) Antibodies: A Laboratory Manual, Cold Spring HarborLaboratory, Cold Spring Harbor; Peters et al. (1985) MonoklonaleAntikorper: Herstellung und Charakterisierung, Springer Verlag) withmyeloma cells to create hybridoma cells producing monoclonal antibodies(MAb), and subsequently suitable clones are isolated. The desiredMAb-producing clones are selected using specific screening methods. Inthese the binding specificity of the antibodies released into the cellculture supernatant, for example for the immunization antigen, apossible carrier of the immunization antigen, pCT, free calcitonin, freekatacalcin and free N-procalcitonin, is tested using, for example,enzyme immunoassays, radioimmunoassays and/or Western blots. Hybridomasproducing the antibodies according to the invention are cloned. Thehybridoma cell lines obtained in this way are then available forcontinuous MAb production. Larger quantities of antibodies may beobtained from, for example, cell culture supernatant, in particular fromfermenters or roller cultures and from ascites.

[0037] It is advantageous depending on the desired purpose to employonly antibody fragments such as, for example, Fab, F(ab′)₂ or Fab′fragments. These may be created, for example, by enzymatic cleavagemethods known to the skilled worker (see also e.g. Harlow & Lane (1988)Antibodies: A Laboratory Manual, Cold Spring Harbor Laboratory, ColdSpring Harbor).

[0038] The antigen binding sites of an antibody are located in theso-called variable domains coded for by the V genes. Using well-knowngenetic engineering methods (see e.g. Sambrook et al. (1989) MolecularCloning: A Laboratory Manual, Cold Spring Harbor Laboratory, Cold SpringHarbor, 2^(nd) edition; McCafferty et al. (1990) Nature 348:552-554) itis also possible to determine the corresponding nucleic acid sequence ofan antibody according to the invention and thereby also thecorresponding amino acid sequence, if not already known from amino acidsequencing. For analyses of this kind, the hybridoma cells or theantibody producing immune cells of immunized animals may be employed asstarting material.

[0039] Knowing the nucleic acid sequence and/or amino acid sequence itis then possible using conventional genetic engineering and molecularbiology methods (see also Johnson & Chiswell (1993) Current Opinion inStructural Biology, 3:564-571) to prepare humanized, chimeric, bi- oroligo-specific antibodies and peptides derived from the complementaritydetermining region (minimal recognition units), single-chain fragmentsand/or functional fusion products, for example recombinantantibody-enzyme constructs (see e.g. Larrick & Fry (1991) HumanAntibodies and Hybridomas, 2:172-189; Kitano et al. (1986) Appl.Microbiol. Biotechnol., 24:282-286; Thompson et al. (1986) J. Immunol.Methods, 94:7-12) which bind to procalcitonin but not to freecalcitonin, free katacalcin and free N-procalcitonin. Using suchpeptides included in the term “antibody” it is possible, for example, toachieve a decrease in immunogenicity and/or an enhanced efficiency whenadministered as a medicament or in vivo diagnostic agent and/or therewill be advantages when employed as or as part of an in vitro diagnosticagent. The antibodies may also be prepared using, where appropriate,genetic engineering methods in plant cells such as, for example, yeastcells (Fischer et al. (1999) Biol. Chem., 380:825-839; Hiatt et al.(1992) Genetic Engineering, 14:49-64)), animal and prokaryotic cells(see e.g. WO 95/25172) and isolated human cells.

[0040] Furthermore, this invention also relates to animal, plant orprokaryotic cells and isolated human cells producing an antibodyaccording to the invention.

[0041] It is also possible for the skilled worker by providing theantibodies according to the invention to identify, for example bycompetition experiments (see also Peters et al. (1985) MonoklonaleAntikörper, Springer Verlag, chapter 12.2 “Epitop-Analyse”), otherspecific binding partners expressly including antibodies which bind tothe epitope of an antibody according to the invention. Thus it ispossible now by techniques known to the skilled worker to selectspecific binding partners using phage display libraries, syntheticpeptide databases or recombinatorial antibody libraries (Larrick & Fry(1991) Human Antibodies and Hybridomas, 2:172-189).

[0042] A “specific binding partner” means a member of a specific bindingpair. The members of a specific binding pair are two molecules eachhaving at least one structure complementary to a structure of the othermolecule, the two molecules being able to bind to each other via bindingof the complementary structures. The term molecule also comprisesmolecule complexes such as, for example, enzymes comprising apoenzymeand coenzyme, proteins comprising a plurality of subunits, lipoproteinscomprising protein and lipids, etc. Specific binding partners may benaturally occurring substances but also substances prepared by means of,for example, chemical synthesis, microbiological techniques and/orgenetic engineering processes. Examples which may be mentioned toillustrate but not restrict the term specific binding partner are:thyroxine binding globulin, steroid binding proteins, antibodies,antigens, haptens, enzymes, lectins, nucleic acids, repressors,oligonucleotides and polynucleotides, protein A, protein G, avidin,streptavidin, biotin, complement component C1q, nucleic acid bindingproteins, etc. Specific binding pairs are for example: antibody/antigen,antibody/hapten, operator/repressor, nuclease/nucleotide, biotin/avidin,lectin/polysaccharide, steroid/steroid binding protein, activeingredient/active ingredient receptor, hormone/hormone receptor,enzyme/substrate, IgG/protein A, complementary oligonucleotides orpolynucleotides, etc.

[0043] This invention also relates to the use of the polypeptidesaccording to the invention in affinity chromatography, in particular forpurifying specific binding partners binding to pCT.

[0044] The term “affinity chromatography” means a method by whichsubstances, in particular biopolymers, are purified and isolated andwhich is based on the fact that many substances can bind to theirspecific binding partners in a selective, noncovalent, reversiblemanner. The principle of the process involves the specific bindingpartner being bound in general covalently to an insoluble matrix (e.g.porous glasses, gels based on agarose, cellulose, dextran, polymer andsilica gel) and brought into contact with a sample containing thesubstance. The sought-after substance is immobilized and retained by itsspecific interaction with the matrix-bound specific binding partner,while all other substances contained in the sample are removed byelution. The sought-after biopolymer is then detached from the matrixusing a suitable eluent which cancels out the noncovalent bond betweensubstance and specific binding partner (see also E. Buddecke (1989)Grundrisse der Biochemie, Walter de Gruyter, chapter 7 “Proteine”).

[0045] This invention additionally relates to the use of thepolypeptides according to the invention and/or the antibodies accordingto the invention as a diagnostic agent, as an ingredient of a diagnosticagent, for preparing a diagnostic agent, as a medicament, as aningredient of a medicament and/or for preparing a medicament.

[0046] The term “diagnostic agent” means in accordance with thisinvention an agent serving in particular to diagnose possible diseases,establish the state of health, the physical or mental state of organismsand/or detect or quantify substances or organisms in samples. In case ofa “in vitro diagnostic agent” the analyte to be detected, for exampleprocalcitonin or anti-procalcitonin antibodies, is detected in a sampleoutside a living human or animal organism and/or the concentration oramount thereof is determined. The polypeptides according to theinvention and/or the antibodies according to the invention may also beadministered to an organism as “in vivo diagnostic agent” in unlabeledor labeled form using, for example, a radioactive isotope in the courseof a function test or a scintigraphic method, for example.

[0047] The polypeptides according to the invention may be processedfurther into, for example, physiologically active pCT cleavage productssuch as, in particular, calcitonin in order to prepare a medicamentwhich may be used to influence calcium and bone metabolism. In addition,the polypeptides according to the invention themselves or else theantibodies according to the invention may be administered as medicamentseither on their own or together with one or more pharmacologicallyactive substances, for example for the treatment of tumors, sepsisand/or SIRS. The polypeptides according to the invention or else theantibodies according to the invention may also have their activityenhanced by modifications and/or linking to pharmacologically activesubstances.

[0048] This invention additionally comprises the polypeptides accordingto the invention and/or the antibodies according to the invention in apharmaceutically suitable sterile injection medium. A pharmaceuticallysuitable sterile injection medium means, for example, a sterilepyrogen-free solution, for example saline or another electrolytesolution, such as is used conventionally in the intravenous,intramuscular, intraperitoneal or subcutaneous administration ofmedicaments, vaccines or contrast media.

[0049] The polypeptides according to the invention and/or the antibodiesaccording to the invention may also be used in particular in a processfor the quantitative or qualitative detection of an analyte, preferablyprocalcitonin or anti-procalcitonin antibodies, in a sample. In such adetection method according to the invention the polypeptides accordingto the invention may serve, for example, as standard antigen and/orspecific binding partner in an analyte/binding partner complex.

[0050] In a quantitative test the amount or the concentration of theanalyte in the sample is measured. The term “quantitative test” alsocomprises semi-quantitative methods which may measure only theapproximate amount or concentration of the analyte in the sample orserve only to indicate relative quantities or concentrations. Aqualitative test means detecting the presence of the analyte in thesample in fact or indicating that the analyte concentration in thesample is below or above a particular threshold or several particularthresholds.

[0051] The term “analyte” means the substance to be detected. Examplesof an analyte are listed in EP-A2-0 515 194 on pages 8-15.

[0052] A “sample” in accordance with the invention means the materialpresumably containing the substance to be detected. The term samplecomprises, for example, biological fluids or tissue, in particular ofhumans and animals such as blood, plasma, serum, sputum, exudate,bronchoalveolar lavage, lymph fluid, synovial fluid, seminal fluid,vaginal mucus, feces, urine, CSF, hairs, skin, tissue samples or tissuesections. Further comprised are cell culture samples, plant fluids ortissue, forensic samples, water and waste water samples, foods,medicaments. The samples need to be pretreated where appropriate to makethe analyte available for the detection method or to remove interferingsample constituents. Such a pretreatment of samples may include removaland/or lysis of cells, precipitation, hydrolysis or denaturation ofsample constituents such as, for example, proteins, centrifugation ofsamples, treatment of the sample using organic solvents such as, forexample, alcohols, in particular methanol; treatment of the sample usingdetergents. Often the sample is transferred into another, usuallyaqueous, medium which, if possible, ought not to interfere with theassay.

[0053] The detection according to the invention of an analyte with thepolypeptides according to the invention and/or the antibodies accordingto the invention may be carried out by methods such as, for example:Western blot, dot blot, immunohistochemical test methods,immunoelectrophoresis, immunofixation electrophoresis,electroimmunodiffusion, immunoprecipitation, radial immunodiffusion,immunofixation, immunochromatography, latex agglutination, turbidimetricor nephelometric test, homogeneous or heterogeneous binding assay, one-or two-step assay, sandwich assay, indirect assay, competitive assay,point-of-care tests, etc. These and other detection methods aredescribed, for example, in “Labor und Diagnose”, ed. L. Thomas, TH-BooksVerlagsgesellschaft mbH, Frankfurt, 1998, chapter 60, or in “LaboratoryTechniques in Biochemistry and Molecular Biology—An Introduction toRadioimmunoassay and Related Techniques”, ed. T. Chard, Elsevier,Amsterdam, 1987.

[0054] In binding assays the analyte, if present in the sample, is boundto one or more analyte-specific binding partners, andanalyte/analyte-specific binding partner(s) complexes are formed.

[0055] In homogeneous binding assays free and complex-bound analytes arenot separated. Examples of homogeneous immunoassays (see also Boguslaski& Li (1982) Applied Biochemistry and Biotechnology, 7:401-414) are manyturbidimetric or nephelometric methods, it being possible for thespecific binding partners used for the detection to be associated withlatex particles; EMIT® assays; CEDIA® assays; fluorescence polarizationimmunoassays; luminescent oxygen channeling immunoassays (EP-A2-0 515194; Ullman et al. (1994) Proc. Natl. Acad. Sci., 91:5426-5430; Ullmanet al. (1996) Clinical Chemistry, A2:1518-1526); etc.

[0056] Heterogeneous binding assays comprise one or more separationsteps and/or wash steps. The separation may be carried out by, forexample, immunoprecipitation, precipitation using substances such aspolyethylene glycol or ammonium sulfate, filtration, magneticseparation, binding to a solid phase such as, for example, to a testtube, a bead, a well of a microtiter plate or to filter paper orchromatography paper. In heterogeneous binding assays frequently onespecific binding partner is associated with a reporter system componentand one specific binding partner is associated with a solid phase(regarding indirect binding see also EP-A2-0 411 945). Here the specificbinding partners may be different or the same, for example ananalyte-specific monoclonal antibody may be employed both as captureagent (for example as a solid-phase antibody) and as labeled antibody ifthe analyte contains more than one epitope.

[0057] In heterogeneous sandwich assays the analyte is usually bound bya specific binding partner associated with a solid phase and a specificbinding partner associated with a reporter system component. In the caseof a sandwich immunoassay the specific binding partners may beanalyte-specific antibodies or, if the analyte itself is an antibody,the antigen and/or a “modified antigen”, for example a labeled antigen,antigen fragment, antigen analog. Examples of such sandwich complexesare: solid-phase antibody< >analyte< >antibody label or solid-phaseantigen< >analyte (=antibody)< >antigen label.

[0058] A further embodiment of a heterogeneous immunoassay is theindirect immunoassay: in this case the analyte is an antibody. One ofthe specific binding partners is the antigen thereof and/or a modifiedantigen and the other specific binding partner is an antibody binding tothe analyte and/or an immunoglobulin-binding protein. Examples of suchcomplexes which may be formed in an indirect immunoassay are:solid-phase anti-IgM antibody< >analyte(=anti-HBsAg IgM)< >HBsAg labelor solid-phase HBsAg<>analyte(=anti-HBsAg IgG)<>protein A label.

[0059] In a heterogeneous competitive immunoassay the sample analytecompetes with a “modified analyte”, for example a labeled analyte,analyte fragment, analyte analog, etc. for a limited number ofanalyte-specific binding sites. Examples illustrating the principle are:(i) sample analyte competes with an analyte associated with a reportersystem component for binding to a solid-phase associatedanalyte-specific antibody or (ii) sample analyte competes with asolid-phase associated analyte for binding to an analyte-specificantibody associated with a reporter system component.

[0060] Sandwich assays, competitive assays and indirect assays may alsobe carried out as homogeneous assay methods (see also EP-A2-0 515 194).

[0061] The term “point-of-care tests” or “POC tests” has a broadmeaning. It includes tests which do not need a separate analyzing ormeasuring device for carrying out or analysing the test. In many casesPOC tests are based on immunochromatography methods, immune complexseparations by filtration and/or immunofixation techniques. POC testsare intended in particular for on-the-spot measurements, for example atthe hospital bed or at home, for the emergency doctor and/or the generalpractitioner and not so much for the large-scale laboratory. POC testsmay also be carried out in particular by persons without in-depthtraining in medical technology and experience in the field of laboratorymedicine. The term “POC tests” in accordance with this invention alsomeans so-called home tests or OTC tests which may be carried out bymedical lay-persons such as, for example, the various pregnancy testssold for home use. Further POC tests relate to, for example, thedetection of heart attack markers, drugs, medicaments, infection markersand inflammation markers. In many POC tests specific binding partnersare associated to filter or chromatography strips or disks during thecourse of the test. A positive or negative test reaction may be linked,for example, to the appearance or nonappearance of a colored band in aparticular test field and/or the appearance or nonappearance of aparticular symbol, for example “+”, “−” and/or the intensity of therespective measured signal.

[0062] A POC test for pCT, for example, may be constructed in thefollowing way: the sample and labeled antibodies according to theinvention which are capable of binding pCT are applied to a test strip.Suitable labels are, for example, colored latex particles, colloidalgold, enzymes, etc. If pCT is present in the sample, PCT/antibodycomplexes will be formed. These complexes move by means of capillaryforce toward a section where antibodies capable of binding to differentpCT epitopes are fixed, for example as a band, or will be fixed duringthe course of the test (for example via a biotin/avidin bridge). Thelabeled PCT/antibody complexes are bound in this section and form asandwich complex with the fixed antibodies. The intensity of the labelsignal is proportional to the pCT sample concentration in this case. Ina competitive POC test method polypeptides according to the inventionmay be fixed, for example, in a section of the test strip or will befixed in the course of the test. The fixed polypeptides according to theinvention would compete with pCT from the sample for binding to labeledanti-pCT antibodies. Alternatively, fixed anti-pCT antibodies andlabeled polypeptides according to the invention may also be employed forconstructing a competitive pCT test.

[0063] A particularly preferred embodiment of the process according tothe invention is a nephelometric or turbidimetric test, in particular atest which employs antibodies according to the invention and/orpolypeptides according to the invention associated to latex particles. Afurther preferred process is a competitive assay in which thepolypeptides according to the invention are associated to a solid phaseand/or a reporter system component.

[0064] This invention further relates to polypeptides according to theinvention associated to a solid phase and/or a reporter systemcomponent. In addition, the antibodies according to the invention mayalso be associated to a solid phase and or a reporter system component.

[0065] The term “associated” has a broad meaning and comprises, forexample, covalent and noncovalent binding, direct and indirect binding,adsorption to a surface and enclosure in a depression or cavity, etc. Inthe case of covalent binding the polypeptides according to the inventionand/or antibodies according to the invention are bound to the solidphase or label via a chemical bond. Examples of noncovalent binding aresurface adsorption, enclosure in cavities or binding of two specificbinding partners. Apart from directly binding to the solid phase or thelabel, the polypeptides according to the invention and/or the antibodiesaccording to the invention may also be bound indirectly to the solidphase or the label through specific interaction with other specificbinding partners (see also EP-A2-0 411 945). This is to be illustratedin more detail with examples: the biotinylated polypeptide according tothe invention may be bound to the label via label-bound avidin; or aconjugate of fluorescein and polypeptide according to the invention maybe bound to the solid phase via solid-phase bound anti-fluoresceinantibodies; or the antibody according to the invention may be bound tothe solid phase or the label via immunoglobulin-binding proteins.

[0066] The term “solid phase” in accordance with this inventioncomprises an object which consists of porous and/or non porous,generally water-insoluble material and which may have very diverseshapes such as, for example, vial, test tube, microtiter plate, bead,microparticle, stick, strip, filter paper or chromatography paper, etc.In general the surface of the solid phase is hydrophilic or may be madehydrophilic. The solid phase may comprise very diverse materials suchas, for example, inorganic and/or organic materials, syntheticmaterials, naturally occurring materials and/or modified naturallyoccurring materials. Examples of solid-phase materials are polymers suchas, for example, cellulose, nitrocellulose, cellulose acetate, polyvinylchloride, polyacrylamide, cross-linked dextran molecules, agarose,polystyrene, polyethylene, polypropylene, polymethacrylate or nylon;ceramics; glass; metals, in particular noble metals such as gold andsilver; magnetite; mixtures or combinations thereof; etc. The term solidphase also comprises cells, liposomes or phospholipid vesicles.

[0067] The solid phase may have a coating of one or more layers of, forexample, proteins, carbohydrates, lipophilic substances, biopolymers,organic polymers or mixtures thereof in order to suppress or prevent,for example, nonspecific binding of sample constituents to the solidphase or to achieve, for example, improvements in suspension stabilityof particulate solid phases, shelf life, shaping stability or resistanceto UV light, microbes or other destructive agents.

[0068] A “reporter system” may be one or more components, at least onecomponent being a detectable label. A label means any molecule producinga signal by itself or capable of inducing production of a signal suchas, for example, a fluorescent substance, radioactive substance, enzymeor chemiluminescent substance. The signal may be detected or measured,for example, by the enzyme activity, luminescence, light absorption,light scattering, electromagnetic or radioactive emission or a chemicalreaction.

[0069] A label may be able to produce a detectable signal by itself sothat no further components are necessary. Many organic molecules absorbultraviolet and visible light, it being possible for these molecules toreach an excited energy level due to the energy transferred by lightabsorption and to emit the absorbed energy as light of a wavelengthdifferent from that of the incident light. Yet other labels may producedirectly a detectable signal such as, for example, radioactive isotopesor dyes.

[0070] Yet other labels need additional components for signalproduction, that is to say the signal producing system in that caseincludes all components needed for generating the signal such as, forexample, substrates, coenzymes, quenchers, accelerators, additionalenzymes, substances reacting with enzyme products, catalysts,activators, cofactors, inhibitors, ions, etc.

[0071] Suitable labels (see also EP-A2-0 515 194; U.S. Pat. No.5,340,716; U.S. Pat. No. 5,545,834; Bailey et al. (1987) J.Pharmaceutical & Biomedical Analysis 5:649-658) are, for example,enzymes including horseradish peroxidase, alkaline phosphatase,glucose-6-phosphate dehydrogenase, alcohol dehydrogenase, glucoseoxidase, β-galactosidase, luciferase, urease and acetylcholinesterase;dyes; fluorescent substances including fluorescein isothiocyanate,rhodamine, phycoerythrin, phycocyanin, ethidium bromide,5-dimethylaminonaphthalene-1-sulfonyl chloride and fluorescent rareearth chelates; chemiluminescent substances including luminol,isoluminol, acridine compounds, olefin, enol ether, enamine, aryl vinylether, dioxene, arylimidazole, lucigenin, luciferin and aequorin;sensitizers including eosin, 9,10-dibromoanthracene, methylene blue,porphyrin, phthalocyanin, chlorophyll, Rose Bengal; coenzymes; enzymesubstrates; radioactive isotopes including ¹²⁵I, ¹³¹I, ¹⁴C, ³H, ³²P,³⁵S, ¹⁴C, ⁵¹Cr, ⁵⁹Fe, ⁵⁷Co and ⁷⁵Se; particles including magneticparticles or particles, preferably latex particles, which may be labeledthemselves by, for example, dyes, sensitizers, fluorescent substances,chemiluminescent substances, isotopes or other detectable labels; solparticles including gold and silver sols; liposomes or cells which maybe labeled themselves by detectable labels; etc.

[0072] A reporter system may also comprise components which can interactwith each other in a detectable manner at close range, for example asenergy donors and energy acceptors such as, for example,photosensitizers and chemiluminescent substances (EP-A2-0 515 194),photosensitizers and fluorophores (WO 95/06877), radioactive iodine-125and fluorophores (Udenfriend et al. (1985) Proc. Natl. Acad. Sci.82:8672-8676), fluorophores and fluorophores (Mathis (1993) Clin. Chem.39:1953-1959) or fluorophores and fluorescence quenchers (U.S. Pat. No.3,996,345).

[0073] An interaction between the components includes direct energytransfer between the components, for example by light or electronradiation and via short-lived reactive chemical molecules. It furthercomprises also processes in which the activity of one component isinhibited or enhanced by one or more others, for example inhibition ofor increase in enzyme activity or inhibition of, increase or change inelectromagnetic radiation emitted from the affected component (e.g.wavelength shift, polarization). The interaction between the componentsalso comprises enzyme cascades. In this case the components are enzymes,at least one of which supplies the substrate for a second one, resultingin maximum or minimum reaction velocity of the coupled substrateconversion.

[0074] An effective interaction between the components generally takesplace when these are in spatial proximity, that is, for example, withina distance of a few μm, in particular within a distance of below 600 nm,preferably below 400 nm, very particularly preferably below 200 nm.

[0075] Microparticles are commonly used as solid phase and/or label. Theterm “microparticle” in accordance with this invention means particleshaving an approximate diameter of at least 20 nm and no more than 20 μm,usually between 40 nm and 10 μm, preferably between 0.1 and 10 μm,particularly preferably between 0.1 and 5 μm, very particularlypreferably between 0.15 and 2 μm. The microparticles may be shapedregularly or irregularly. They may comprise spheres, spheroids, sphereshaving more or less large cavities or pores. The microparticles maycomprise organic material, inorganic material or a mixture orcombination of both. They may comprise porous or nonporous material,swellable or non-swellable material. In principle the microparticles mayhave any density, however, particles having a density close to thedensity of water such as from about 0.7 to about 1.5 g/ml are preferred.The preferred microparticles are suspendable in aqueous solutions andstable in suspension for as long as possible. They may be transparent,partly transparent or opaque. The microparticles may comprise aplurality of layers such as, for example, the so-called core-and-shellparticles having a core and one or more surrounding layers. The termmicroparticle comprises, for example, dye crystals, metal sols, silicaparticles, glass particles, magnetic particles, polymer particles, oildrops, lipid particles, dextran, and protein aggregates. Preferredmicroparticles are particles suspendable in aqueous solutions andcomprising water-insoluble polymer material, in particular substitutedpolyethylenes. Very particularly preferred are latex particles made of,for example, polystyrene, acrylic acid polymers, methacrylic acidpolymers, acrylonitrile polymers, acrylonitrile/butadiene/styrene,polyvinyl acetate-acrylate, polyvinylpyridine, vinyl chloride/acrylate.Of particular interest are latex particles having on their surfacereactive groups such as, for example, carboxyl, amino or aldehyde groupswhich facilitate covalent binding, for example of specific bindingpartners, to the latex particles. The preparation of latex particles isdescribed in, for example, EP 0 080 614, EP 0 227 054 and EP 0 246 446.

[0076] The invention further relates to a test kit containing one ormore of the antibodies according to the invention and/or one or more ofthe polypeptides according to the invention. Such a kit usually containsall or only some test components in packaged form. The antibodiesaccording to the invention and the polypeptides according to theinvention may be associated to, for example, one or more solid phasesand/or one or more reporter system components. The test kit may contain,for example, standards; controls; and further reagents such as, forexample, buffers, washing solutions, measured signal inducing solutionsand/or enzyme substrate; cuvettes; pipettes and/or instructions. Aparticularly preferred test kit according to the invention containspolypeptides according to the invention and/or antibodies according tothe invention associated to latex particles.

[0077] A particularly preferred embodiment of the invention is the useof the polypeptides according to the invention in standards and/orcontrols. In detection methods the concentration, amount or activity ina sample of a substance to be detected is commonly determined usingreference or standard curves. In order to obtain such reference curves,standards, also called calibrators, containing a specific knownconcentration, amount or activity of the analyte are measured in thedetection method. In the end, the concentration, amount or activity ofthe analyte in the sample can be determined by comparing the measuredsignal values of the sample with the reference curve.

[0078] Controls contain similarly to the standards a specific knownconcentration, amount or activity of the analyte or a modified analyteand serve to check the detection method.

[0079] To prepare the standards and/or controls according to theinvention a specific amount of one or more of the polypeptides accordingto the invention is added to a matrix. This matrix may be, for example ahuman or animal serum or plasma or even an artificial matrix such as,for example, a buffer which may contain proteins and which may alsocontain further substances. Standards and controls may also contain oneor more additional analytes. They can be in liquid, frozen orlyophilized form and therefore may be employed in the detection methodseither directly or only after preparation.

[0080] The invention further relates to stable pCT solutions which maybe used, for example, as controls, standards or else for other in vitroand in vivo applications. “Stable” in this connection means that thedesired property of the procalcitonin present in the solution, forexample the ability to bind to specific antibodies remains generallyunchanged over a specific period, in particular during liquid storage,while in “unstable” pCT solutions this property changes significantlyover the same period.

[0081] Stable pCT solutions can be prepared by adding the polypeptidesand sterol esters according to the invention to aserum/plasma-containing or serum/plasma-free matrix.

[0082] Particularly in pCT solutions employed as pCT controls and/or pCTstandards the employed pCT may also be, for example, a peptide which hasbeen isolated from natural sources or produced by recombination andwhich contains at least considerable parts of the amino acid sequence ofhuman pCT such as, for example, relatively large pCT cleavage products.However, the peptide has to be suitable as standard and/or control serumantigen in a quantitative or qualitative pCT detection method.

[0083] The sterol esters suitable for preparing the pCT solutionaccording to the invention belong to the steroid class of substances(gonane derivatives) which is generally characterized by an hydroxylgroup in the 3 β position. The main differences are on the side chainlocated in the 17(20) position. The sterols constitute a large class(Beyer et al. (1981), Lehrbuch der organischen Chemie, pp 649-664“Steroide”). Advantageously vitamin D3, estrone, stigmasterol and,particularly advantageously, cholesterol and derivatives thereof may beused.

[0084] The sterol esters to be employed according to the inventionadditionally and preferably have a polyethylene glycol group (PEG group)linked via a dicarboxylic acid. In principle all known dicarboxylicacids may be used; the use of succinic acid, adipic acid or sebacic acidis particularly advantageous.

[0085] In addition, the PEG group essentially ought to ensure thesolubility of the sterol ester, so that the skilled worker is able todetermine the optimal length easily, if necessary in an experiment. Fromexperience the following chain lengths are advantageous: polyethyleneglycol 600, polyethylene glycol 900 or polyethylene glycol 3000.

[0086] The sterol esters preferably employed for preparing the pCTsolutions according to the invention are of the general formula I:

[0087] where n =1-200 and

[0088] R₁ is sterol,

[0089] R₂ is an aliphatic or aromatic ring of 4 to 8 carbon atoms,wherein one or more of the ring atoms is optionally replaced by N, S orO, or is a linear aliphatic carbon chain having from 0 to 12 carbonatoms, or is a branched aliphatic carbon chain having from 0 to 12carbon atoms, wherein 0 carbon atoms represents a bond; particularlypreferred is the use of sterol esters in which R₁ is a compound of thegeneral formula II:

[0090] where R₄ and R₅ may be H or —CH₃, R₆ is selected from a linearcarbon chain having from 1 to 12 carbon atoms, a branched carbon chainhaving from 1 to 12 carbon atoms, an -OH group, and a =O group; and therings A, B, C and D are each independently saturated, unsaturated oraromatic, and, if R₄ is —C(19)H₃, ring B may be opened between C(9) andC(10) with formation of a double bond between C(9) and C(19).

[0091] Very particularly preferred is the use of sterol esters, wherethe sterol residue originates from cholesterol, vitamin D3, stigmasterolor estrone. Advantageously the sterol ester is added in a concentrationsuch that the concentration in the pCT solution is 0.05-5% by weight,preferably 0.1-3% by weight, particularly preferably 0.5-1.5% by weight.

[0092] The pCT solutions according to the invention may also containprotease inhibitors, for example aprotinin, benzamidine, bestatin,cystatin, pepstatin, PMSF, trypsin inhibitor, and/or detergents, inparticular nonionic and/or zwitterionic detergents.

[0093] A particularly preferred embodiment of the pCT solution apartfrom the sterol esters also contains polygeline. Polygeline is a mixtureof thermally degraded and cross-linked gelatin proteins and may beprepared according to DE-A 1155134 or U.S. Pat. No. 3,057,782.Advantageously polygeline is added such that the concentration in thepCT solution is 0.1-10% by weight, preferably 1-8% by weight,particularly preferably 2-6% by weight.

[0094] In order to measure the stabilizing effect—in particular in pCTsolutions serving as standards and/or controls—pCT may be determined,for example, in a nephelometric measurement method.

[0095] A further embodiment of this invention comprises the use ofstandards, controls and pCT solutions according to the invention inmethods for quantitative or qualitative detection of pCT, calcitonin,katacalcin, N-procalcitonin and/or further pCT fragments in a sample.

[0096]FIG. 1 shows the amino acid sequence of human pCT.

[0097]FIG. 2 shows the amino acid sequence of a polypeptide according tothe invention without (A) and with (B) fusion segment.

[0098]FIG. 3 shows the nucleic acid sequence of vector pQE-30 (3462 basepairs)

[0099]FIG. 4 shows the nucleic acid sequence of the insert which codesfor pCT and which was cloned into pQE-30 including the cleavage sitesused.

[0100]FIG. 5 shows the nucleic acid sequence of human pCT.

[0101] The examples described below serve as exemplary illustrations ofindividual aspects of this invention and are not to be understood as arestriction.

EXAMPLES

[0102] 1. Cloning of Procalcitonin

[0103] The N terminus of pCT (see FIG. 1) was constructed by means ofsynthetic oligonucleotides while the construction of the C terminus wascarried out by PCR (polymerase chain reaction) on the basis of genomicDNA of human placenta:

[0104] (i) N Terminus

[0105] The following two oligonucleotides were used as primers: 1094:5′ GTG GGA TCC GCA CCA TTC AGG TCT GCC CTG GAG AGC AGC CCA GCA GAC CCGGCC ACG CTC AGT GAG GAC GAA GCG CGC CTC CTG CTG GCT GCA CTG GTG CA 3′1095′: 5′ GTG AAG CTT AGA TCT GGG GCT GTC CAG GCT GGA GCC CTC TCT CTCTTG CTC CTG CTC CAG CTC ACT GGC CTT CAT CTG CAC ATA GTC CTG CAC CAG TGCAGC CA 3′

[0106] where the respective 16 3′ terminal nucleotides werecomplementary to each other.

[0107] The following PCR was carried out:

[0108] 0.25 mM dNTP (Amersham Pharmacia, Freiburg, Germany), 1 μM eachof primers 1094 and 1095, 10 mM Tris HCl, pH 8.3, 50 mM KCl, 1.5 mMMgCl₂, 0.001% gelatin, 2.5 U Ampli-Taq DNA polymerase (Perkin Elmer,Branchburg, N.J.) were pipetted into a 50 μl reaction mixture and wereamplified by means of the Perkin Elmer thermocycler GenAmp 9700 (allfurther PCR reactions were carried out in the same apparatus) accordingto the following temperature program:

[0109] initial: 94° C. 5 min,

[0110] 5× cycle: 94° C. 30 s, 52° C. 30 s and 72° C. 30 s,

[0111] terminal: 72° C. 10 min.

[0112] 5 μl of this mixture were transferred into a fresh 50 μl mixtureas above but using the primers 1098 and 1099 1098: 5′ GTG GGA TCC GCACCA TTC 3′ 1099: 5′ GTG AAG CTT AGA TCT GGG GC 3′

[0113] and the reaction was carried out using the following temperatureprogram:

[0114] initial: 94° C. 5 min,

[0115] 30× cycle: 94° C. 30 s, 56° C. 30 s and 72° C. 30 s,

[0116] terminal: 72° C. 10 min.

[0117] 5 μl of this mixture were ligated with 0.5 μg of vector pCR2.1from the Invitrogen TA cloning kit in accordance with the manufacturer'sinstructions and transformed into E.coli INVαF′. The newly constructedplasmid was isolated and sequenced using standard methods and, duringthe course of this, an L to R amino acid exchange at position 37 ofprocalcitonin was found.

[0118] (ii) C Terminus

[0119] Genomic DNA was isolated from 2 g of human placental tissue usingstandard methods (all protocols described as standard methods are from“Current Protocols in Molecular Biology”, 1995, Wiley & Sons Inc., NewYork, USA) and employed as template for the following PCR:

[0120] 0.5 μg (1 μl) of human genomic DNA as template and 1 μg each ofprimers 1100 and 1101 were pipetted into a 50 μl reaction mixtureaccording to the manufacturer's instructions for the Taq PCR core kit,cat. No: 201223 (Qiagen, Hilden, Germany) 1100: 5′ GTG TCT AGA TCT AAGCGG 3′ 1101: 5′ GTG AAG CTT TTA GTT GGC 3′

[0121] and amplified according to the following temperature program:

[0122] initial: 94° C. 3 min,

[0123] 30× cycle: 94° C. 30 s, 45° C. 30 s and 72° C. 30 s,

[0124] terminal: 72° C. 10 min.

[0125] 5 μl of this mixture were ligated with 0.5 μg of vector pCR2.1from the Invitrogen TA cloning kit in accordance with the manufacturer'sinstructions and transformed into E.coli INVαF′. The novel plasmid wasisolated and sequenced using standard methods, confirming the presenceof the wild-type sequence.

[0126] (iii) Construction of the Expression Plasmid

[0127] 1 μg of vector pQE-30 (Qiagen) was opened using restrictionendonucleases BamHI and HindIII (all restriction endonucleases werepurchased from Boehringer Mannheim, Mannheim, Germany). In addition, theN terminus was excised from the plasmid pCR2.1 containing the N terminususing BamHI and HindIII (BamHI and HindIII had been artificiallyintroduced by the PCR), isolated using standard methods and ligated intothe opened pQE-30 vector. The construct was isolated and opened usingBglII and HindIII (BglII is naturally present at the 3 end of the Nterminus and could be employed here for the construction). Finally, theC terminus was excised from the vector pCR2.1 containing the C terminususing BglII and HindIII, isolated using standard methods and ligatedinto the pQE-30 vector opened by BglII and HindIII and alreadycontaining the N terminus. The clone containing the correct plasmid wasidentified and the construct was verified by sequencing. The insert usedfor the construction and extending from BamHI to HindIII is shown inFIG. 4; the natural human pCT sequence is shown in FIG. 5.

[0128] 2. Expression of Procalcitonin

[0129] The expression of procalcitonin was first carried out on thesmall scale of 1 ml:

[0130] 1 ml of LB medium (Current Protocols in Molecular Biology)containing 50 μg of ampicillin (Sigma, Deisenhofen, Germany) wasinoculated with a single colony of E. coli strain JM109 harboring theexpression plasmid and induced at an OD₆₀₀ of 0.4 with 1 mM IPTG(isopropyl thiogalactoside, Sigma) for 2 h. Unexpectedly, strongexpression of the fusion protein of human pCT and the N-terminal segmentMRGSHHHHHHGS of the pQE vector was found when the total protein of theculture was analyzed in a Coomassie-stained PAGE gel (Current Protocolsin Molecular Biology).

[0131] Thereafter, expression was carried out on a larger scale usingstandard conditions, i.e. an overnight culture of a single clone was setup in 100 ml of LB medium containing 50 μg/ml ampicillin and shaken at37° C. This culture was grown until stationary and then diluted 1:50 in1 l of fresh LB medium (ampicillin 50 μg/ml), further a shaken at 37° C.and induced at an OD₆₀₀ of 0.6 with 1 mM IPTG for 3 h.

[0132] Surprisingly, a drastic decline or a complete stop of fusionprotein expression was detected in this case. This negative result wasreproducible, leading to the conclusion that the fusion protein is toxicfor E. coli and there is very rapid selection of mutants which do notexpress the fusion protein or express it only very poorly. Therefore anattempt was made to optimize the expression.

[0133] In this context the strain used for expression was varied (JM109,M15, BL21 and W3110 (Stratagene, La Jolla, Calif.) changing, theselection pressure level was varied by changing the ampicillinconcentration, the strength of induction was varied by changing theinduce IPTG and the expression time was varied by monitoring thestrength of induction time course after induction.

[0134] The following optimal parameters were found thereby:

[0135] JM109 cells freshly transformed with the expression plasmid weregrown with shaking overnight in LB medium with 100 μg/ml ampicillin at37° C. and then diluted 1:50 in 1 l of fresh LB medium (ampicillin 100μg/ml) and further shaken at 37° C. and induced at an OD₆₀₀ of 0.4 with2 mM IPTG for 3 h.

[0136] By following these optimized conditions about 13 mg of fusionprotein were reproducibly obtained from a 1 l culture after purificationunder native conditions by metal affinity chromatography according tothe manufacturer's instructions (Talon Metal Affinity Resin, Clontech,Palo Alto, Calif.) and subsequent gel filtration on Superdex™ 75 HiLoad(Amersham Pharmacia).

[0137] 3. Amino Terminal Sequencing

[0138] The amino terminal sequence of recombinant human procalcitoninwas determined by automatic Edman degradation in an Applied Biosystems477A sequencer.

[0139] The amino terminal sequence found is identical after the pQEvector sequence to that found for pCT from a human thyroid tumor (J. M.Conlon et al. (1988) Biochem. J. 256:245-250) (see Table 1). TABLE 1Amino terminal sequence of human pCT and recombinant human pCT ProteinAmino acid sequence Reference Human pCT (thyroid tumor)A-P-F-R-S-A-L-E-S-S-P Conlon et al. (1988) Rec. human pCTM-R-G-S-H-H-H-H-H-H-G-S-A-P-F-R-S-A-L-E-S-S-P This invention   *

[0140] 4. Relative Molecular Mass Determination by Mass Spectrometry

[0141] The determination of the relative molecular mass of the preparedrecombinant procalcitonin was carried out by means of electrospray massspectrometry. Recombinant pCT obtained after expression and purificationwas dialyzed against distilled water and measured at a concentration of50 μμg/ml in methanol/water/acetic acid (50/50/0.1) (orifice voltage 90V; ion spray voltage 5000 V).

[0142] The mean molecular mass of recombinant human pCT calculated fromthe obtained spectrum is 14,235±2 dalton.

[0143] The result corresponds very well with the theoretical mass of14,239 dalton calculated on the basis of the theoretical amino acidsequence (J. M. Conlon et al. (1988) Biochem. J., 256:245-250) andtaking into account the pQE vector fusion segment (pQE vector:MRGSHHHHHHGS) and the amino acid exchange at position 37 (L to R) andtherefore confirms the expression of recombinant human pCT.

[0144] 5. Determination of Reactivity in a LUMItest® PCT

[0145] The LUMItest® PCT (B.R.A.H.M.S, Berlin, Germany) is animmunoluminometric assay for determining procalcitonin. Two monoclonalantibodies binding to procalcitonin at two different sites (calcitoninand katacalcin segments) are employed here.

[0146] After performing the assay according to the manufacturer'sdescription, the luminescence signals are determined in a suitableluminometer. The size of the luminescence signal is directlyproportional to the pCT concentration of the respective sample. From theluminescence signal values for the accompanying standards a standardcurve can be constructed, from which the unknown procalcitonin sampleconcentration may be read off.

[0147] Recombinant pCT obtained after expression and purification wasdetermined in two different dilutions in a LUMItest® PCT according tothe manufacturer's instructions (see Table 2). TABLE 2 Measured valuesdetermined in a BeriLux ® Analyzer 250 (RLU = relative light units)Sample RLU ng pCT/ml Standard S1 72 0.08 Standard S2 169 0.49 StandardS3 467 1.94 Standard S4 6643 20.5 Standard S5 97085 212 Standard S6215415 527 Rec. pCT dil. 1 18742 50.41 Rec. pCT dil. 2 1056 4.46

[0148] The following pCT content according to LUMItest® PCT iscalculated for the two samples examined, taking into account the twodilutions employed (1:10,000 and 1:100,000).

[0149] Rec. pCT dil. 1: 0.5041 mg/ml

[0150] Rec. pCT dil. 2: 0.4463 mg/ml

[0151] This investigation provides support for the identity ofrecombinant pCT and human pCT and shows the usability of rec. pCT, forexample as standard and/or control serum material in a diagnostic assayfor determining human pCT.

[0152] 6. Preparation of Monoclonal Antibodies Against Recombinant pCT

[0153] (i) Immunization of Mice

[0154] BALB/c mice are immunized intraperitoneally with 20 μg of rec.pCT in complete Freund's adjuvant. A booster of 20 μg of rec. pCT inincomplete Freund's adjuvant (ICN Biomedical GmbH, Eschwege, Germany)follows after 4 weeks and another booster of 20 μg of rec. pCT withoutFreund's adjuvant after 8 weeks. On the last three days before fusionthe mice are boosted intravenously each day by 20 μg of recombinant pCT.

[0155] (ii) Fusion

[0156] After killing the mice by CO₂ inhalation the spleens were removedand single cell suspensions were prepared in serum-free Dulbecco'smodified Eagle medium (DMEM, CC Pro GmbH, Neustadt/W, Germany). Thecells were centrifuged (652× g) and washed twice in DMEM. Subsequentlythe cell number was determined by means of trypan blue staining. 2×10⁷myeloma cells (Sp2/0) were added to about 10⁸ spleen cells. Aftercentrifugation (360× g) the supernatant was discarded, 1 ml ofpolyethylene glycol solution (PEG 4000, Merck Eurolab, Bruchsal,Germany; ca. 50% in DMEM) was added to the cell pellet, and theresuspended cells were incubated for 1 minute at 37° C. About 10 ml ofDMEM were subsequently added dropwise and incubated at room temperaturefor 2 to 4 minutes. The fused cells were spun down (326× g) and thepellet was resuspended in DMEM+20% FBS (fetal bovine serum, BioWhittakerEurope, Verviers, Belgium)+HAT solution (CC Pro GmbH, Neustadt/W,Germany) and introduced into 24-well cell culture dishes (Costar). Theapproximate cell concentration per well was 5×10⁴ to 5×10⁶.

[0157] 2-3 weeks later the resulting cell colonies (hybrids) wereremoved and transferred into new culture dishes.

[0158] (iii) Specificity Assay

[0159] The specificity of the antibodies released into the cell culturewas tested in a first step using microtiter plates coated withimmunization antigen (Nunc, type B), coating 0.2 μg/ml≈0.003 μg/well.

[0160] 100 μl of cell culture supernatant (dilution 1:2) were pipettedinto each well of the microtiter plate and incubated at +15 to +25° C.for 1 hour. After washing the plate twice using washing solution POD(OSEW; Dade Behring, Marburg, Germany) 100 μl of anti-mouseIgG/F(ab′)₂-POD conjugate (Dade Behring, Marburg, Germany) wereintroduced into each well and incubated at +15 to +25° C. for 1 hour.After washing the plate twice again 100 μl of Chromogen TMB solution(Dade Behring, Marburg, Germany) were introduced into each well andincubated at +15 to +25° C. for a further 30 minutes. After theincubation, 100 μl of stop solution POD (Dade Behring, Marburg, Germany)were introduced into each well and the microtiter plate was analyzed at450 nm in a BEP II (Behring ELISA Processor II).

[0161] In a 2nd step the hybrids were tested as described above usingmicrotiter plates (Nunc, type B) coated with the following peptides:

[0162] i. Recombinant human pCT (0.03 jig/well)

[0163] ii. Calcitonin human BSA conjugate (0.5 μg/well, Bachem, prod.No.: H-2250)

[0164] iii. Katacalcin human (PDN-21) BSA conjugate (0.5 μg/well,Peninsula, prod. No.: 6004)

[0165] iv. Calcitonin N-terminal flanking peptide BSA conjugate (0.5μg/well, Bachem, prod. No.: H-3076) human N-procalcitonin

[0166] The results are listed in Table 3. TABLE 3 Determination ofantibody specificity by analyzing the microtiter plates at 450 nm in aBEP II (Behring ELISA Processor II). Extinction at 450 nm Recombinanthuman N-procalci- Hybrid/(clone) procalcitonin Calcitonin Katacalcintonin 99-41/14 (032) 2.5 0.834 0.068 0.025 99-41/5 (05) 2.5 0.010 2.50.014 99-246/58 2.5 0.032 0.030 2.246

[0167] (iv) Cloning

[0168] Single hybrid cells producing the antibodies according to theinvention (binding to human pCT) were cloned using a micromanipulator(Leitz, Wetzlar, Germany).

[0169] (v) Antibody Subclass Determination

[0170] The antibody subclass is determined by means of theIsoStrip™-Mouse Monoclonal Antibody Isotyping Kit from BoehringerMannheim, Germany.

[0171] (vi) Antibody Production

[0172] For the production of larger quantities of the antibodiesaccording to the invention the corresponding cell clones are transferredto roller bottles (Corning Costar Deutschland, Bodenheim) and expandedto the desired final volume at +37° C. Afterward, the roller culturesuspension is filtered through 0.22 μm to remove the cells. The nowcell-free antibody solution is concentrated via ultrafilters (30kilodalton cutoff) and subsequently purified.

[0173] (vii) Antibody Purification

[0174] The antibody solution obtained is pH-adjusted with 0.14 Mphosphate buffer pH 8.6 and applied to a chromatography column packedwith rProtein A Sepharose Fast Flow (Amersham Pharmacia) (1 ml ofrProtein A Sepharose Fast Flow is employed per 10 mg of antibody to bepurified). All unbound components are removed by washing the column in0.14 M phosphate buffer pH 8.6. The bound antibody is eluted from thecolumn by 0.1 M citric acid pH 3.0 and dialyzed against 0.05 M sodiumacetate+0.5 M NaCl+0.05 M tris+0.01% sodium azide pH 7.0.

[0175] 7. Detection of pCT in a Sample

[0176] (i) MAb Binding to Latex Particles

[0177] One each of a monoclonal anti-calcitonin antibody according tothe invention and of a monoclonal anti-katacalcin antibody according tothe invention was bound to latex particles prepared according to EP-0246446 and having a diameter of from 250 to 310 nm:

[0178] The latex polymer used was diluted to a solids content of 4% byweight using distilled water. The antibodies to be bound were diluted toa protein content of 5 mg/ml using 0.05 M sodium acetate+0.5 M NaCl+0.05M tris+0.01% sodium azide pH 7.0. 1 ml of the abovementioned polymer wasmixed with 200 μl of antibody solution. Then 0.050 ml of a 20% Tween 20solution (Merck Eurolab, Darmstadt, Germany) was added and the mixturewas mixed again. 0.025 ml of 1 N HCl was added thereto resulting in a pHof about 3. After incubation at room temperature for 30 minutes, 0.25 mlof 1 M phosphate buffer pH 6.5 and 0.25 ml of sodium cyanoborohydride(25 mg/ml) were added and mixed well. This was followed by incubation atroom temperature for one hour.

[0179] This loading mixture was then centrifuged at about 50,000 g for30 minutes. The supernatant was discarded. The residue was resuspendedin 4 ml of imidazole buffer pH 8.1 (5 g/l imidazole, 40 g/l sucrose, 1g/l human albumin). This was followed by sonication (Branson SonifierB15) for 30 seconds. The reagent redispersed in this way was diluted ina volume ratio of 1:7.5 using the imidazole buffer mentioned before andsonicated again for 30 seconds.

[0180] (ii) Preparation of a Standard/Control

[0181] The protein content of recombinant pCT obtained after expressionand purification was determined in the preparation by means of a proteindetermination according to Lowry et al. (1951, J. Biol. Chem. 193,265-275). In order to prepare a standard, a suitable amount of thispreparation was taken up in phosphate-buffered saline with 10 g/l bovineserum albumin, and the recombinant pCT content was calculated.

[0182] (iii) Detection of pCT

[0183] The reagents prepared according to Example 7(i) by binding of theanti-calcitonin antibody according to the invention and theanti-katacalcin antibody according to the invention to latex particleswere mixed in a volume ratio of 1+1 and employed for measuring pCT in astandard and in the sera of patients in a Behring Nephelometer Analyser(BNA, Dade Behring, Marburg, Germany). The mixed reagent is agglutinatedwhen mixed with pCT-containing samples. The intensity of the scatteredlight in the BNA is dependent on the sample pCT concentration, so thatthe pCT concentration in the sample can be determined by comparison withdilutions of a standard of known concentration. The Behring NephelometerAnalyser automatically makes the necessary standard dilutions usingN-Diluens (Dade Behring, Marburg, Germany). The measured result isautomatically calculated using a logit-log function. For the measurement100 μl of sample or standard are mixed with 100 μl of N-Diluens (DadeBehring, Marburg, Germany) and 40 μl of the mixed reagent in a reactioncuvette and the change in the measured signal (in bit) is measured inthe BNA after 12 minutes. The results are summarized in Table 4. TABLE 4Standard curve and measurement of samples Measured signal Sample BNA inbit ng pCT/ml Standard dilution 1 2727 250*   Standard dilution 2 1972125*   Standard dilution 3 1152 62.5* Standard dilution 4 450 31.3*Standard dilution 5 157 15.6* Standard dilution 6 54  7.8* Standarddilution 7 26  3.9* Standard dilution 8 14  2.0* Normal serum −188<2.0   pCT-containing serum 1 219 19.3  pCT-containing serum 2 770 46.3 pCT-containing serum 3 1594 90.7  pCT-containing serum 4 627 39.6 pCT-containing serum 5 43  6.3 

[0184] 8. Preparation of a Stable pCT Solution

[0185] (i) Preparation of the pCT Solution

[0186] In order to prepare the pCT solution particularly suitable asstandard and/or control, a suitable amount of recombinant pCT obtainedafter expression and purification was taken up in different matrices.

[0187] Matrix 1:

[0188] Phosphate-buffered saline pH 7.2+1 g/l NaN₃+40 g/l Polygeline(Hoechst Marion Roussel Deutschland GmbH, prod. No.: 125590)+80,000kIU/l Antagosan® (active ingredient: aprotinin, Hoechst Marion RousselDeutschland GmbH, prod. No.: 122162)

[0189] Matrix 2:

[0190] Phosphate-buffered saline pH 7.2+1 g/l NaN₃₊₄₀ g/l Polygeline(Hoechst Marion Roussel Deutschland GmbH, prod. No.: 125590)+80,000kIU/l Antagosan® (active ingredient: aprotinin, Hoechst Marion RousselDeutschland GmbH, prod. No.: 122162)+10 g/l cholesterol, water-soluble(Sigma, order No.: C-1145)

[0191] Matrix 3:

[0192] Lipoprotein-free human citrate plasma (prepared according toExample 4 of EP-0 606 616)+1 g/l NaN₃+80,000 kIU/l Antagosan® (activeingredient: aprotinin, Hoechst Marion Roussel Deutschland GmbH, prod.No.: 122162)

[0193] Matrix 4:

[0194] Lipoprotein-free human citrate plasma (prepared according toExample 4 of EP-0 606 616)+1 g/l NaN₃+80,000 kIU/l Antagosan® (activeingredient: aprotinin, Hoechst Marion Roussel Deutschland GmbH, prod.No.: 122162)+10 g/l cholesterol, water-soluble (Sigma, order No.:C-1145)

[0195] (ii) Stability Test

[0196] In order to test its stability, the pCT solution was stored at+2° C. to +8° C. and, after different storage periods, the change in themeasured signal (in bit) of the pCT detection method according toExample 7(iii) was determined. The results are summarized in Table 5.TABLE 5 Shelf life of pCT solutions pCT solution (125 ng/ml) MeasuredMeasured signal Deviation signal Deviation BNA in in % from BNA in in %from bit after measured bit measured Measured 3 weeks signal after 8signal signal BNA of BNA in weeks of BNA in in bit storage bit afterstorage bit after after at +2° C.- prep- at +2° C.- prep- preparation+8° C. aration +8° C. aration Matrix 1 1629  489 −70 — — Matrix 2 19161959 2.2 1821 −5.0 Matrix 3 1840 1321 −28.2 — — Matrix 4 1757 1324 −24.6— —

[0197] Result: The pCT solution based on matrix 2 is particularlystable. The addition of cholesterol also promotes the stability of pCTin serum/plasma matrix.

1 12 1 101 DNA Unknown Organism Description of Unknown Organism Primer,non genomic DNA 1 gtgggatccg caccattcag gtctgccctg gagagcagcc cagcagacccggccacgctc 60 agtgaggacg aagcgcgcct cctgctggct gcactggtgc a 101 2 104DNA Unknown Organism Description of Unknown Organism Primer, non genomicDNA 2 gtgaagctta gatctggggc tgtccaggct ggagccctct ctctcttgct cctgctccag60 ctcactggcc ttcatctgca catagtcctg caccagtgca gcca 104 3 18 DNA UnknownOrganism Description of Unknown Organism Primer, non genomic DNA 3gtgggatccg caccattc 18 4 20 DNA Unknown Organism Description of UnknownOrganism Primer, non genomic DNA 4 gtgaagctta gatctggggc 20 5 18 DNAUnknown Organism Description of Unknown Organism Primer, non genomic DNA5 gtgtctagat ctaagcgg 18 6 18 DNA Unknown Organism Description ofUnknown Organism Primer, non genomic DNA 6 gtgaagcttt tagttggc 18 7 116PRT Unknown Organism Description of Unknown Organism Protein, humanprocalcitonin 7 Ala Pro Phe Arg Ser Ala Leu Glu Ser Ser Pro Ala Asp ProAla Thr 1 5 10 15 Leu Ser Glu Asp Glu Ala Arg Leu Leu Leu Ala Ala LeuVal Gln Asp 20 25 30 Tyr Val Gln Met Lys Ala Ser Glu Leu Glu Gln Glu GlnGlu Arg Glu 35 40 45 Gly Ser Ser Leu Asp Ser Pro Arg Ser Lys Arg Cys GlyAsn Leu Ser 50 55 60 Thr Cys Met Leu Gly Thr Tyr Thr Gln Asp Phe Asn LysPhe His Thr 65 70 75 80 Phe Pro Gln Thr Ala Ile Gly Val Gly Ala Pro GlyLys Lys Arg Asp 85 90 95 Met Ser Ser Asp Leu Glu Arg Asp His Arg Pro HisVal Ser Met Pro 100 105 110 Gln Asn Ala Asn 115 8 116 PRT UnknownOrganism Description of Unknown Organism Protein, human procalcitonin 8Ala Pro Phe Arg Ser Ala Leu Glu Ser Ser Pro Ala Asp Pro Ala Thr 1 5 1015 Leu Ser Glu Asp Glu Ala Arg Leu Arg Leu Ala Ala Leu Val Gln Asp 20 2530 Tyr Val Gln Met Lys Ala Ser Glu Leu Glu Gln Glu Gln Glu Arg Glu 35 4045 Gly Ser Ser Leu Asp Ser Pro Arg Ser Lys Arg Cys Gly Asn Leu Ser 50 5560 Thr Cys Met Leu Gly Thr Tyr Thr Gln Asp Phe Asn Lys Phe His Thr 65 7075 80 Phe Pro Gln Thr Ala Ile Gly Val Gly Ala Pro Gly Lys Lys Arg Asp 8590 95 Met Ser Ser Asp Leu Glu Arg Asp His Arg Pro His Val Ser Met Pro100 105 110 Gln Asn Ala Asn 115 9 128 PRT Unknown Organism Descriptionof Unknown Organism Protein, human procalcitonin 9 Met Arg Gly Ser HisHis His His His His Gly Ser Ala Pro Phe Arg 1 5 10 15 Ser Ala Leu GluSer Ser Pro Ala Asp Pro Ala Thr Leu Ser Glu Asp 20 25 30 Glu Ala Arg LeuArg Leu Ala Ala Leu Val Gln Asp Tyr Val Gln Met 35 40 45 Lys Ala Ser GluLeu Glu Gln Glu Gln Glu Arg Glu Gly Ser Ser Leu 50 55 60 Asp Ser Pro ArgSer Lys Arg Cys Gly Asn Leu Ser Thr Cys Met Leu 65 70 75 80 Gly Thr TyrThr Gln Asp Phe Asn Lys Phe His Thr Phe Pro Gln Thr 85 90 95 Ala Ile GlyVal Gly Ala Pro Gly Lys Lys Arg Asp Met Ser Ser Asp 100 105 110 Leu GluArg Asp His Arg Pro His Val Ser Met Pro Gln Asn Ala Asn 115 120 125 103462 DNA Unknown Organism Description of Unknown Organism Vectorsequence, DNA 10 ctcgagaaat cataaaaaat ttatttgctt tgtgagcgga taacaattataatagattca 60 attgtgagcg gataacaatt tcacacagaa ttcattaaag aggagaaattaactatgaga 120 ggatcgcatc accatcacca tcacggatcc gcatgcgagc tcggtaccccgggtcgacct 180 gcagccaagc ttaattagct gagcttggac tcctgttgat agatccagtaatgacctcag 240 aactccatct ggatttgttc agaacgctcg gttgccgccg ggcgttttttattggtgaga 300 atccaagcta gcttggcgag attttcagga gctaaggaag ctaaaatggagaaaaaaatc 360 actggatata ccaccgttga tatatcccaa tggcatcgta aagaacattttgaggcattt 420 cagtcagttg ctcaatgtac ctataaccag accgttcagc tggatattacggccttttta 480 aagaccgtaa agaaaaataa gcacaagttt tatccggcct ttattcacattcttgcccgc 540 ctgatgaatg ctcatccgga atttcgtatg gcaatgaaag acggtgagctggtgatatgg 600 gatagtgttc acccttgtta caccgttttc catgagcaaa ctgaaacgttttcatcgctc 660 tggagtgaat accacgacga tttccggcag tttctacaca tatattcgcaagatgtggcg 720 tgttacggtg aaaacctggc ctatttccct aaagggttta ttgagaatatgtttttcgtc 780 tcagccaatc cctgggtgag tttcaccagt tttgatttaa acgtggccaatatggacaac 840 ttcttcgccc ccgttttcac catgggcaaa tattatacgc aaggcgacaaggtgctgatg 900 ccgctggcga ttcaggttca tcatgccgtc tgtgatggct tccatgtcggcagaatgctt 960 aatgaattac aacagtactg cgatgagtgg cagggcgggg cgtaatttttttaaggcagt 1020 tattggtgcc cttaaacgcc tggggtaatg actctctagc ttgaggcatcaaataaaacg 1080 aaaggctcag tcgaaagact gggcctttcg ttttatctgt tgtttgtcggtgaacgctct 1140 cctgagtagg acaaatccgc cgctctagag ctgcctcgcg cgtttcggtgatgacggtga 1200 aaacctctga cacatgcagc tcccggagac ggtcacagct tgtctgtaagcggatgccgg 1260 gagcagacaa gcccgtcagg gcgcgtcagc gggtgttggc gggtgtcggggcgcagccat 1320 gacccagtca cgtagcgata gcggagtgta tactggctta actatgcggcatcagagcag 1380 attgtactga gagtgcacca tatgcggtgt gaaataccgc acagatgcgtaaggagaaaa 1440 taccgcatca ggcgctcttc cgcttcctcg ctcactgact cgctgcgctcggtctgtcgg 1500 ctgcggcgag cggtatcagc tcactcaaag gcggtaatac ggttatccacagaatcaggg 1560 gataacgcag gaaagaacat gtgagcaaaa ggccagcaaa aggccaggaaccgtaaaaag 1620 gccgcgttgc tggcgttttt ccataggctc cgcccccctg acgagcatcacaaaaatcga 1680 cgctcaagtc agaggtggcg aaacccgaca ggactataaa gataccaggcgtttccccct 1740 ggaagctccc tcgtgcgctc tcctgttccg accctgccgc ttaccggatacctgtccgcc 1800 tttctccctt cgggaagcgt ggcgctttct caatgctcac gctgtaggtatctcagttcg 1860 gtgtaggtcg ttcgctccaa gctgggctgt gtgcacgaac cccccgttcagcccgaccgc 1920 tgcgccttat ccggtaacta tcgtcttgag tccaacccgg taagacacgacttatcgcca 1980 ctggcagcag ccactggtaa caggattagc agagcgaggt atgtaggcggtgctacagag 2040 ttcttgaagt ggtggcctaa ctacggctac actagaagga cagtatttggtatctgcgct 2100 ctgctgaagc cagttacctt cggaaaaaga gttggtagct cttgatccggcaaacaaacc 2160 accgctggta gcggtggttt ttttgtttgc aagcagcaga ttacgcgcagaaaaaaagga 2220 tctcaagaag atcctttgat cttttctacg gggtctgacg ctcagtggaacgaaaactca 2280 cgttaaggga ttttggtcat gagattatca aaaaggatct tcacctagatccttttaaat 2340 taaaaatgaa gttttaaatc aatctaaagt atatatgagt aaacttggtctgacagttac 2400 caatgcttaa tcagtgaggc acctatctca gcgatctgtc tatttcgttcatccatagct 2460 gcctgactcc ccgtcgtgta gataactacg atacgggagg gcttaccatctggccccagt 2520 gctgcaatga taccgcgaga cccacgctca ccggctccag atttatcagcaataaaccag 2580 ccagccggaa gggccgagcg cagaagtggt cctgcaactt tatccgcctccatccagtct 2640 attaattgtt gccgggaagc tagagtaagt agttcgccag ttaatagtttgcgcaacgtt 2700 gttgccattg ctacaggcat cgtggtgtca cgctcgtcgt ttggtatggcttcattcagc 2760 tccggttccc aacgatcaag gcgagttaca tgatccccca tgttgtgcaaaaaagcggtt 2820 agctccttcg gtcctccgat cgttgtcaga agtaagttgg ccgcagtgttatcactcatg 2880 gttatggcag cactgcataa ttctcttact gtcatgccat ccgtaagatgcttttctgtg 2940 actggtgagt actcaaccaa gtcattctga gaatagtgta tgcggcgaccgagttgctct 3000 tgcccggcgt caatacggga taataccgcg ccacatagca gaactttaaaagtgctcatc 3060 attggaaaac gttcttcggg gcgaaaactc tcaaggatct taccgctgttgagatccagt 3120 tcgatgtaac ccactcgtgc acccaactga tcttcagcat cttttactttcaccagcgtt 3180 tctgggtgag caaaaacagg aaggcaaaat gccgcaaaaa agggaataagggcgacacgg 3240 aaatgttgaa tactcatact cttccttttt caatattatt gaagcatttatcagggttat 3300 tgtctcatga gcggatacat atttgaatgt atttagaaaa ataaacaaataggggttccg 3360 cgcacatttc cccgaaaagt gccacctgac gtctaagaaa ccattattatcatgacatta 3420 acctataaaa ataggcgtat cacgaggccc tttcgtcttc ac 3462 11363 DNA Unknown Organism Description of Unknown Organism DNA sequence,human procalcitonin 11 ggatccgcac cattcaggtc tgccctggag agcagcccagcagacccggc cacgctcagt 60 gaggacgaag cgcgcctccg gctggctgca ctggtgcaggactatgtgca gatgaaggcc 120 agtgagctgg agcaggagca agagagagag ggctccagcctggacagccc cagatctaag 180 cggtgcggta atctgagtac ttgcatgctg ggcacatacacgcaggactt caacaagttt 240 cacacgttcc cccaaactgc aattggggtt ggagcacctggaaagaaaag ggatatgtcc 300 agcgacttgg agagagacca tcgccctcat gttagcatgccccagaatgc caactaaaag 360 ctt 363 12 351 DNA Unknown OrganismDescription of Unknown Organism DNA sequence, human procalcitonin 12gcaccattca ggtctgccct ggagagcagc ccagcagacc cggccacgct cagtgaggac 60gaagcgcgcc tcctgctggc tgcactggtg caggactatg tgcagatgaa ggccagtgag 120ctggagcagg agcaagagag agagggctcc agcctggaca gccccagatc taagcggtgc 180ggtaatctga gtacttgcat gctgggcaca tacacgcagg acttcaacaa gtttcacacg 240ttcccccaaa ctgcaattgg ggttggagca cctggaaaga aaagggatat gtccagcgac 300ttggagagag accatcgccc tcatgttagc atgccccaga atgccaacta a 351

1. An isolated polypeptide preferably prepared by means of genetic engineering processes and comprising the amino acid sequence of human procalcitonin APFRSALESS PADPATLSED EARLLLAALV QDYVQMKASE LEQEQEREGS SLDSPRSKRC GNLSTCMLGT YTQDFNKFHT FPQTAIGVGA PGKKRDMSSD LERDHRPHVS MPQNAN
 2. An isolated polypeptide preferably prepared by means of genetic engineering processes and comprising the amino acid sequence APFRSALESS PADPATLSED EARLRLAALV QDYVQMKASE LEQEQEREGS SLDSPRSKRC GNLSTCMLGT YTQDFNKFHT FPQTAIGVGA PGKKRDMSSD LERDHRPHVS MPQNAN
 3. The isolated polypeptide as claimed in claim 2 comprising the amino acid sequence MRGSHHHHHHGS APFRSALESS PADPATLSED EARLRLAALV QDYVQMKASE LEQEQEREGS SLDSPRSKRC GNLSTCMLGT YTQDFNKFHT FPQTAIGVGA PGKKRDMSSD LERDHRPHVS MPQNAN
 4. A process for preparing human procalcitonin wherein a gene coding for a polypeptide comprising the amino acid sequence of human procalcitonin is inserted into a vector; a host organism is transformed with this gene-containing vector; and the polypeptide expressed by the host organism is isolated.
 5. The process as claimed in claim 4 wherein the polypeptide is prepared as claimed in one of claims 1-3.
 6. The process as claimed in claim 4 or 5 wherein the host organism is a human, animal, plant or prokaryotic cell, preferably an E. coli cell.
 7. The process as claimed in one of claims 4-6 wherein the vector codes for a fusion segment, preferably polyhistidine, which later on permits a simple purification of the procalcitonin fusion protein.
 8. The process as claimed in one of claims 4-7 wherein the vector used is pQE-30.
 9. The process as claimed in one of claims 4-8 wherein metal affinity chromatography and/or gel filtration are employed for isolating the polypeptide.
 10. A plasmid comprising one or more nucleic acid sequences coding for one or more of the polypeptides as claimed in claims 1-3.
 11. The plasmid as claimed in claim 10 having the deposition number DSM
 13203. 12. An animal, plant, isolated human or prokaryotic cell which is able to express a polypeptide as claimed in one of claims 1-3.
 13. A polypeptide as claimed in one of claims 1-3 or a product of a process as claimed in one of claims 4-9 in a pharmaceutically suitable, sterile injection medium.
 14. A polypeptide as claimed in one of claims 1-3 or a product of a process as claimed in one of claims 4-9 for use as a diagnostic agent, as an ingredient of a diagnostic agent and/or for preparing a diagnostic agent.
 15. A polypeptide as claimed in one of claims 1-3 or a product of a process as claimed in one of claims 4-9 for use as a medicament, as an ingredient of a medicament and/or for preparing a medicament.
 16. A polypeptide as claimed in one of claims 1-3 or a product of a process as claimed in one of claims 4-9 for use as an immunogen for preparing antibodies.
 17. A process for preparing antibodies wherein one or more polypeptides as claimed in one of claims 1-3 are used as immunization antigen and/or one or more products of a process as claimed in one of claims 4-9 are used as immunogen.
 18. The use of a polypeptide as claimed in one of claims 1-3 or a product of a process as claimed in one of claims 4-9 in affinity chromatography.
 19. The use of a polypeptide as claimed in one of claims 1-3 or a product of a process as claimed in one of claims 4-9 in a method for quantitative or qualitative detection of an analyte, preferably procalcitonin or anti-procalcitonin antibodies.
 20. A polypeptide as claimed in one of claims 1-3 or a product of a process as claimed in one of claims 4-9 associated with a solid phase and/or a reporter system component.
 21. The use of a polypeptide as claimed in one of claims 1-3 or a product of a process as claimed in one of claims 4-9 in standards and/or controls.
 22. A test kit containing one or more polypeptides as claimed in one of claims 1-3 and/or one or more products of a process as claimed in one of claims 4-9.
 23. A control and/or standard comprising one or more polypeptides as claimed in one of claims 1-3 and/or one or more products of a process as claimed in one of claims 4-9.
 24. A solution comprising one or more polypeptides as claimed in one of claims 1-3 and/or one or more products of a process as claimed in one of claims 4-9 and one or more sterol esters of the general formula I:

where n=1-200 and R₁ is sterol, R₂ is an aliphatic or aromatic ring of 4 to 8 carbon atoms, wherein one or more of the ring carbon atoms is optionally replaced by N, S, or O, or is a linear aliphatic carbon chain having from 0 to 12 carbon atoms, or is a branched aliphatic carbon chain having from 0 to 12 atoms, wherein 0 carbon atoms represents a bond.
 25. A solution as claimed in claim 24 where R₁ is a compound of the general formula II:

where R₄ and R₅ may be H or CH₃, R₆ may be selected from a linear carbon chain having from 1 to 12 carbon atoms, a branched carbon chain having from 1 to 12 carbon atoms, an —OH group, and a ═O group; and the rings A, B, C and D are each independently saturated, unsaturated or aromatic and, if R₄ is —C(19)H₃, ring B may be opened between C(9) and C(10) with formation of a double bond between C(9) and C(19).
 26. A solution as claimed in claim 24 wherein R₁ is selected from the group: cholesterol, vitamin D3, stigmasterol and estrone.
 27. A solution as claimed in one of claims 24-26, wherein the sterol ester concentration is from 0.05% by weight to 5% by weight.
 28. A solution as claimed in one of claims 24-27 wherein the solution additionally contains polygeline.
 29. A solution as claimed in claim 28 wherein the polygeline concentration is from 0.1% by weight to 10% by weight. 